The present invention relates generally to biosynthetic processes, and more specifically to organisms having propylene biosynthetic capability.
Propylene is produced primarily as a by-product of petroleum refining and of ethylene production by steam cracking of hydrocarbon feedstocks. Propene is separated by fractional distillation from hydrocarbon mixtures obtained from cracking and other refining processes. Typical hydrocarbon feedstocks are from non-renewable fossil fuels, such as petroleum, natural gas and to a much lesser extent coal. Over 75 billion pounds of propylene are manufactured annually, making it the second largest fossil-based chemical produced behind ethylene. Propylene is a base chemical that is converted into a wide range of polymers, polymer intermediates and chemicals. Some of the most common derivatives of chemical and polymer grade propylene are polypropylene, acrylic acid, butanol, butanediol, acrylonitrile, propylene oxide, isopropanol and cumene. The use of the propylene derivative, polypropylene, in the production of plastics, such as injection moulding, and fibers, such as carpets, accounts for over one-third of U.S. consumption for this derivative. Propylene is also used in the production of synthetic rubber and as a propellant or component in aerosols.
The ability to manufacture propylene from alternative and/or renewable feedstocks would represent a major advance in the quest for more sustainable chemical production processes. One possible way to produce propylene renewably involves fermentation of sugars or other feedstocks to produce the alcohols 2-propanol (isopropanol) or 1-propanol, which is separated, purified, and then dehydrated to propylene in a second step involving metal-based catalysis. Direct fermentative production of propylene from renewable feedstocks would obviate the need for dehydration. During fermentative production, propylene gas would be continuously emitted from the fermenter, which could be readily collected and condensed. Developing a fermentative production process would also eliminate the need for fossil-based propylene and would allow substantial savings in cost, energy, and harmful waste and emissions relative to petrochemically-derived propylene.
Microbial organisms and methods for effectively producing propylene from cheap renewable feedstocks such as molasses, sugar cane juice, and sugars derived from biomass sources, including agricultural and wood waste, as well as C1 feedstocks such as syngas and carbon dioxide, are described herein and include related advantages.